The present invention relates to a vibratory packerhead or drycast concrete pipe-forming apparatus and more particularly to improving the transmission of the vibration affect from the vibrating means to the concrete in the mold.
Precast concrete products, such as, for example, non-reinforced or steel reinforced precast concrete pipe or tile, steel-reinforcd precast concrete manhole segments, steel-reinforced precast concrete box culvert segments, non-reinforced or steel-reinforced concrete catch basin structures, and the like typically are manufactured by machinery of various types which are designed and built to manufacture multiple units of like or similar shape and application in a single production run. These products fall into the broad class of concrete pipe products or typically are manufactured by factories whose primary product is concrete pipe. Typically, these precast concrete products are made from various Portland cement mixtures. In the manufacture of concrete pipe or tile, a variety of drycast or packerhead or roller head concrete pipe-forming machines are known. These machines utilize vibration, in whole or in part, as a means to consolidate or densify the cementitious mixture, and as a means to facilitate achievement of the desired concrete surface texture. Such machines can be found in U.S. Pats. Nos. 4,118,165, 4,197,074, 4,235,580, and Re. Pat. No. 28,902, the disclosure of which is incorporated expressly herein by reference.
The application of vibration to the cementitious mixture causes the mixture to assume a more plastic state during the vibration action, so that following the vibration procedure, the resulting vibrating product is in a more consolidated or dense state. Vibration additionally results in the finest components of the mixture or slurry being moved to the molded surfaces, thus achieving the desired surface texture. The effectiveness and efficiency of the vibrating action is dependent upon its application directly to the concrete mixture or to the mixture through a mold or machine component, in the frequency, impact, and amplitude appropriate for achieving the desired result.
Concrete pipe products typically have a tongue or male end and a socket or female end which is bell-shaped. Either end of the pipe product may be adapted to receive a gasket (e.g rubber or other suitable material) for the purpose of achieving a water-tight seal between sections of the pipe when joined. The surface texture and finish of the inner socket end (the surface formed by the upper vertical and horizontal surfaces of the curing pallet) must be adequately compacted to provide the compressive and tensile strength required to resist the force applied by forcing the gasketed end or ends in place. It also is important that the inner concrete surface of the socket end be smooth and void-free to facilitate a water-tight seal. One or both of these two critical conditions frequency are not attained due principally to the failure of the machinery to provide effective vibration during the pipe-forming process.